Punch and die apparatus for producing flat stamped contact devices having improved contact edge surfaces

Abstract

Flat stamped electrical contact device (2) has a contact edge (8,8') which extends from the first major surface (4) to the second major surface (6) of the device. The contact edge surface (8,8') is smooth for substantially its full width and does not have a fractured portion or a burr extending from the second major surface (6). The smooth straight surface is produced by steps of coining the opening produced during the initial punching operation at a location adjacent to the second major surface after the opening has been punched and then shaving the edge to produce the finished contact surface.

We claim: 
     
       1. A punch and die assembly for manufacturing stamped electrical contacts from strip material which has oppositely facing first and second parallel rolled surfaces, each of the contacts having a first and second edge surface which extends substantially normally of, and between, the rolled surfaces to define a hole, the first edge surface being the contact surface of the contact, the punch and die assembly comprising: a punch and die station, a pre-shaving station, a coining station, and a final shaving station,   the punch and die station comprising a punch and die for punching said hole in the strip stock, said first edge surface of the hole being the contact surface, the surfaces of said hole having a flat smooth portion and a fractured portion, the smooth portion extending inwardly from the first rolled surface to the fractured portion, the fractured portion extending from the smooth portion to the second rolled surface,   the pre-shaving station performing a preliminary shaving operation by a shaving tool which is moved against the second rolled surface and partially across the fractured portion of said hole towards the first rolled surface,   the coining station having a coining die which coins, and work hardens the pre-shaved and fractured portion adjacent to the second rolled surface,   the final shaving station having a final shaving tool which shaves the contact surface along a final shaving path which extends from the first rolled surface to the coined portion, whereby,   the final shaving tool produces a smooth shaved surface on the surface of the hole which extends from the first rolled surface to the coined portion, and the coined portion is fractured without plastic deformation and without producing a burr at the second rolled surface.   
     
     
       2. A punch and die assembly as set forth in claim 1 characterized in that the coining die has an inclined coining surface which moves against the intersection of the fractured portion and the second rolled surface and produces a work hardened beveled surface. 
     
     
       3. A punch and die assembly as set forth in claim 1 in combination with a stamping and forming machine which has first and second ram assemblies which move horizontally towards and away from each other, said ram assemblies having opposed faces for receiving said strip material therebetween, whereby the four stations of the punch and die assembly is mounted for reciprocal movement on the first and second ram assemblies, where said coining die is on the second ram assembly, and said final shaving tool is on the first ram assembly. 
     
     
       4. A punch and die assembly as set forth in claim 1 in combination with a stamping and forming machine which has first and second ram assemblies which move horizontally towards and away from each other, said ram assemblies having opposed faces for receiving said strip material therebetween, whereby the four stations of the punch and die assembly are mounted for reciprocal movement on the first and second ram assemblies, where said pre-shaving tool and the coining die are on the second ram assembly, and the final shaving tool is on the first ram assembly. 
     
     
       5. A punch and die assembly as set forth in claim 1 wherein the final shaving tool is dimensioned so as to remove only a very thin shaving on the surface of the hole which extends from the first rolled surface to the coined portion. 
     
     
       6. A punch and die assembly as set forth in claim 1 wherein said pre-shaving tool is dimensioned so as to produce an inwardly directed burr about the surface of said hole.